1. Field of the Invention:
The present invention relates to a centrifugal supercharger and more particularly to a centrifugal supercharger for an engine of a motorcar.
2. Description of the Related Art:
A conventional centrifugal supercharger 70, as shown in FIG. 6, is disclosed in Japanese Magazine "Motor Fan" for December, 1989. In the centrifugal supercharger 70, pulleys 71a, 71b which are driven by an engine (not shown) drive pulleys 72a, 72b via a belt 80. The pulleys 71a, 71b, 72a, 72b and belt 80 compose a CVT (continuous variable transmission) 79 which is known in general.
The pulleys 72a, 72b are rotatably supported on a shaft 74. A plate 81 is fixed to the shaft 74, and is connected with or parted from the right side of the pulley 72b by action of an electromagnetic coil 73. The shaft 74 and a shaft 76 are rotatably supported on a housing 82. A compressor rotor 77 is fixed on the right end of the shaft 76, and is located in an intake passage 78 of the engine.
The shaft 76 is connected with the shaft 74 via a rotating speed step-up or accelerating device 75. Planetary gears 83a, 83b are rotatably supported on shafts 84a, 84b fixed on the housing 82. An outer member 85 is fixed to the right end of the shaft 74, and has an inner gear meshed with the gears 83a, 83b. An inner member 86 is fixed to the left end of the shaft 76, and has an outer gear meshed with the gears 83a, 83b. So, the revolution of the outer member 85 is transmitted to the revolution of the inner member 86 with acceleration by planetary gears 83a, 83b.
The needed revolution of the compressor rotor 77 is about 200,000 .about.300,000 r.p.m. in maximum, and gears are used in the accelerating device 75. So, the noise generated at the gears is very large. Further, the oil for lubricating the gears is stripped off from the gears by centrifugal force. So, the lubricating effect does not act for the gears.